This invention relates generally to valves and more particularly to a non-contaminating and gas-tight valve designed for regulating a flow of granular polysilicon through the valve.
Conventionally, valves of various construction regulate flows of liquid, solid, and semi-solid materials. Common valve types include globe valves, gate valves, check valves, butterfly valves, and ball valves. Each valve type is specifically suited to a particular application. Adjustable ball valves are conventionally used in applications where the valve adjusts between fully open and fully closed. Although not specifically designed to throttle flow, ball valves may be adjusted between open and closed positions to throttle or adjust flow. Ball valves typically contain a metallic, plastic, or ceramic ball, which is rotatable about an axis perpendicular to the flow. A cylindrical channel passes through the center of the ball. When the channel is perpendicular to the flow, the valve is closed. When the channel is parallel to the flow, the valve is open. When the ball is at any point in between, the valve is partially open.
Depending upon the material and environmental requirements, valves are typically constructed of plastic, metal, rubber, and ceramic parts. As with all mechanical apparatus with moving parts, valves are susceptible to wear. Moving parts rubbing against one another and matter flowing through the valve contacting the parts causes valve wear. Dust and particle accumulation on a valve""s moving parts also causes wear during operation. Wear inevitably leads to contamination of the material flowing through the valve by particles generated from the valve wear. Such wear may or may not be acceptable depending upon the purity requirements of the material flowing through the valve. In the semiconductor industry, handling of granular polysilicon requires minimal particulate contamination. As such, conventional valves having metallic or plastic parts have substantial drawbacks when applied to granular polysilicon because foreign particulate matter from the valve as it wears will inevitably contaminate the granular polysilicon. Therefore, there is a need for a valve which (1) is wear resistant and (2) is less apt to cause contamination as a result of wear.
Among the several objects of this invention may be noted the provision of such a valve that avoids generation of metallic particles or other contaminants without compromising sealing integrity; the provision of such a valve that is wear resistant; the provision of such a valve that inhibits the valve from seizing due to excess material accumulating within the valve; the provision of such a valve that has non-contaminating members holding the moving parts of the valve in place; and the provision of such a valve that forms a gas-tight seal between an upstream and downstream side of the valve through a single gas-tight seat placed between the moving valve member and the valve body.
In general, a valve apparatus for controlling a flow of granular polysilicon is disclosed. The valve apparatus inhibits contamination of the granular polysilicon by foreign materials. The valve apparatus comprises a valve body having an inlet and an outlet sized and shaped to allow granular polysilicon to flow into and out of the valve body. The valve apparatus additionally comprises a movable valve member arranged within the valve body for regulating the flow through the valve body. The movable valve member is formed from single-crystal silicon to reduce valve wear and inhibit creation of metal particles or similar contaminants within the flow of granular polysilicon. The movable valve member is movable between an open position where the granular polysilicon may flow through the valve body and a closed position where the granular polysilicon cannot flow through the valve body.
In a second embodiment of the present invention, a valve member formed from single-crystal silicon generally as set forth above is disclosed.
In a final embodiment of the present invention, a granular polysilicon handling system for controlling a flow of granular polysilicon is disclosed. The handling system comprises at least one material hopper sized and shaped to hold granular polysilicon within the system and at least one valve apparatus as set forth above.
Other objects and features will be in part apparent and in part pointed out hereinafter.